Nature can be … weird. If you’ve ever seen a coconut crab or an
aye-aye, then you know exactly what I mean. But recently, researchers have been studying
some animals that even they admit are strange.
For example, a group of paleontologists thinks it’s figured out the evolutionary story
behind one of the weirdest-looking animals that ever lived: the Tully Monster.
Paleontologist Victoria McCoy, now at the University of Leicester, has been fascinated
with this ancient sea creature since she was a child.
She recently described the Tully monster as being “just about at the top of the scale
of weirdness.” But how weird are we talking exactly?
Lemme put it this way: If the cantina in Star Wars had an aquarium, a Tully monster would
fit right in. It looked like it was cobbled together from
the spare parts of random animals, with some extra bits thrown in.
It had a chunky body, eyes sticking out from its head on rigid stalks, and vicious little
teeth inside a mouth shaped like a crab claw, at the end of a long trunk.
Even though it sounds like something out of a George Lucas fever dream, this creature
was very real – it swam around 300 million years ago in what’s now Illinois.
So … what was it? Ever since it was first discovered in the
1950s -- by an amateur fossil hunter named Francis Tully -- scientists have been stumped
by it. But McCoy and her colleagues examined more
than twelve hundred fossilized Tully monsters that’ve been found over the past 60 years,
and they announced last week in the journal Nature, that they had solved the mystery.
For the most part. While studying high-resolution photographs
of all of the known fossils of the creature -- which is officially known as Tullimonstrum
-- they found some crucial features that had been overlooked before.
For example, Tully monsters have a pale band running through the middle of their bodies.
This was originally assumed to be a gut tube – a sort of primordial digestive system
— but that wasn’t very helpful, considering that most animals have some kind of gut.
But gut tubes tend to be much darker when they show up in fossils, and they stop before
reaching the tail, at the anus. But the pale band found in the monsters extended
clear through the tail. Furthermore, some Tully monsters showed two
bands, a dark one and a light one. So the light band had to be something else.
Turns out, it was a rudimentary spinal cord. This meant Tully monsters weren’t giant
worms or slugs... ...they were vertebrates!
With that important clue, the scientists searched branch after branch of the tree of life, looking
for similarities with other creatures. In time, some features that they’d noticed
before began to make more sense. The backward-pointing teeth made of keratin,
for example, and the faint outline of a simple brain, and its single nostril.
All of these traits are shared by Tully monsters and one other known animal: lampreys – long
fish with toothy, jawless mouths. So, McCoy and her colleagues concluded that
Tullimonstrum was probably an ancient relative of lampreys.
But there’s still a lot left to learn about it, from how it might have lived, to why there
aren’t any animals that look much like it today.
--- While we’re on the subject of fish that
are really frickin’ weird … one fish in a UK lab tank did something so unexpected,
it got a whole research paper dedicated to it!
Scientists were keeping a bunch of cichlid fish in isolation, in separate tanks, as part
of a study on species hybridization. And it seems that one of the female fish got
bored or lonely or something, because it apparently fertilized its own eggs, and had dozens of
babies, all by itself. Researchers have called this solo style of
sexual reproduction “selfing”. It turns out that this fish had fourteen broods
of male and female baby fish… without ever mating.
Some of the offspring went on to have babies of their own – produced the regular way.
That means those fish had two parents, but just three grandparents!
But this wasn’t a case of cloning or parthenogenesis -- sometimes called “virgin birth” -- neither
of which requires sperm. Instead, this fish managed to achieve true
self-fertilization, using sperm and egg cells from the same organism.
This kind of reproduction is well-documented in plants and many invertebrates, but among
vertebrates it’s almost unheard of. So, howww does one go about selfing … oneself?
Well, in the cichlid’s case, it managed to develop a functional testis. Basically,
one of its ovaries started producing spermatocytes, the precursors to sperm cells.
So now, scientists are trying to figure out how she managed to pull this off.
Sex determination in cichlid fish is pretty complicated. Each species has its own system,
controlled by genes, the environment, or both. And the fact this fish was a hybrid of two
closely related species further complicates things.
But for now, researchers think that selfing might be a rare evolutionary strategy that
some animals can use to reproduce in a new or changing environment -- places where weird
risks are more likely to pay off. So, thanks Nature. You’re really weird.
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